Sanding machine



April 14, 1931. B. D. PINKNEY SANDING moana:

Filed June 3, 4 1929 2 Sheets-Sheet l fifa/7%; YJ.

April 14, 1931. B. D. PINKNEY SANDING MACHINE Filed June '3, 1929 2 Sheets-Sheet 2 W/ TNESS my, 5. mm ,Y.

2ND! um r y A m ne@ a w Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE BRYAN D. PINKNEY, 0F SMITHVILLE, NEW' JERSEY, ASSIGNOR TO H. `B. SMITH MA- CHINE COMPANY, OF SMITHVILLE, NEW JERSEY, A CORPORATION OF INEXT)l'IFlItSIilY SANDING Application filed .Tune 3,

This invention relates to sanding machines or similar abrading mechanisms and has particular reference to the construction of a drum therefor. i Y Y ln one generally used type of drum two sets of jaws are provided to clamp the respective ends of the abrasive paper or cloth carried by the drum, one of these sets of jaws being adjnstable'and tensioned to take up slack in the abrasive sheet. In order to permit access to the aws, for replacement of the sheet, a relatively wide opening in the drum wall is necessary which results in an interruption of the abrasive surface producing` transverse rotation marks on work being sanded.

It has also been proposed to clamp both ends of the abrasivesheet between the jaws of a single pair. Since the jaws occupied a ixed position in the drum it was necessary to `take up the slack by members `acting on the portions of the abrasive sheet extending from the jaws to the periphery of the drum. This not only necessitated the location of the jaws a substantial distance within the periphery, Where they were inaccessible, but also necessitated the provision of a wide opening as otherwise the members `re'li'erred to could not produce sufficient movement of the portions ofthe sheet with which they contacted to take up the slack.

The primary object of the present invention relates to the provision of abrasive sheet clamping means which facilitate the placement of sheet and which serve to take up lslack therein without disturbing the static or running balance of the drum, the opening of the drum being very small.

Another obj ect of the invention relates to an improved means for securing to the drum a felt or similar backing for the abrasive sheet.

A further object relates to the improved construction of clamping jaws. j j

`Other objects will become apparent from the 'following description read in conjunction with the accompanying drawings in which: Fig. 1 is a view, partly in section, of an end of a sanding drum;

Fig. 2is a fragmentary transverse sectional View of the drum;

:MACHINE 1929. serial No. 367,921.

Fi 3 is aview similar to Fig. 2, illustrating re abrasive sheet clamped in the clamping jaws; j

Fin". 4 is a view similar to Fig. 3 illustrating tie action of the slacktake-up;

Fig. 5 is a sectional viewshowing details of the clamping jaws; and j s F ig. 6 is an end view of the fixed clamping jaw. j j

The drum consists, preferably, of a `plurality of separate sections 2 tted together and securedto a shaft 1. Axially extending openings in the various assembled sections are in alignment and forma receiving opening Gthrough which the ends of an abrasive sheet-extend to` be clamped by suitable jaws hereafter described. One side of the opening, that which `carries the leading end of theabrasive sheet against the work when the drum rotates as indicated by the arrows in Figs. 2 and 3, is formed by a hardened lip 8 secured to ledges formed on the drum sections by screws 10. vThe end of a yielding backing of felt or similar material is clamped between the lip and a clamp 12 secured to the lip by bolts v14:. After securing the backing` as described it is attachedto the surface of the drum with adhesive and carried into the opening 6 at the opposite edge thereof. After the adhesive dries, they backing is trimmed as indicated at 18. 1

Extendingl longitudinally through the sections 2 and journalled therein is a shaft 2O which projects from one end of the drum and is there provided with a squared end so that o it may be rotated by a suitable wrench 22.` A plurality of collars 24: are carried by the shaft, each being provided with an opening receiving` one end of a spiral spring 26 the other end of which `engages a counterbalancing rod V28 extending througha plurality of hinges 30 jonrnalled on shaft 20. The outer end of shaft 20 Vcarries a ratchet 32' engageable by a pawl 34, whereby rotation of the shaft in a clockwise direction, as viewed in Fig. 2, may be prevented. The various element described in this paragraph are similar to those disclosedin the patent to Perry,

j Number 891,857, datedwlune `80, 1908, to

which reference may be made fork details of operation.

Extending along the drum and secured to the hinges 30 is a jaw 36, which will be referred to as a fixed jaw, saidjaw being of angular cross-section, andhaving an outwardly extending clamp 38. An adjustable jaw 40 of similar cross-section has an out? wardly extending clamp 42 arranged to bey moved 'towards and away from clamp 38, the adjacent Vfaces of clamps 42 and 38 Vbeing serrated or grooved to securely grip the ends of the abrasive sheet. Relative movements of the jaws are obtained by reason of the fact that slots 44 are provided in jaw 40 through which extend screws 46 threaded into jaw 36.

Accordingly, if jaw 40 is urged lengthwise,A

its clamp 42 i-s simultaneously carried towards or away from clamp 38 to lclamp or release the ends Vof thelabrasive sheet therefrom. Y In order to conveniently move jaw 40 relatively to jaw 36, the latter is provided with an upstanding end 48 in the upper edge of which is formed a slot 50 serving as a bearing for an adjusting screw 52, threaded as indicated at 54 into an u standing end 56 of jaw 40, and provided with a suitable head 58 adapted to be readily engaged by. an adjusting-tool. ThisY screw adjustrnentisl very advantageous in that the necessary tight engagement of the I jaws with the abrasive sheet is obtained without theV application of violent'force such as hammerfblows which, though necessaryv to secure jaws. heretoforev devised, Vtend to destroy them.- .i f l The operation of the improved take-up devicewill be clear from Figs. 2 and 8. As

shown in the latter figure, the abrasive sheet '60 of sand paper, or the like, is Vdrawn about the drum the ends 62 and 64 thereof being inturnedA overtheedges 66 and 68 respectivelyand clamped betweenthe jaws. The abrasive sheet is, of course, secured while the parts are in the position shcwnin Fig. 2, the tensions on springs 26 havingvbeen relieved rso that the jaws may be arranged as shown inthat figure.. After the sheet is clampedas shown in Fig. 3, shaft 2O is turned in a counterclockwise direction to tensionthe springs and is held by pawl 34 'whereupon slack is taken up with a resultant initial positioning of the jaws somewhere between thel positions shown in Figs. 3 and 4.

' As the drum is now-putv into use, thereaction of the work on the abrasive sheet will stretchit in a direction from edge 68 to edge 66 producing slack at the latter, which will be taken up by movement of thejaws in a counterclockwise direction under the influence of springs 26. Y It willbe noted that asl l the jaws move during this take-up action, Vtheir free ends move in an arcas'indicated in broken lines in Fig. 3 midwayracross a radius joining edge 68 ywith the axis of rotation. At

` the same time, they arevmovingdirectly away free ends from edge 681cha'nges only very slightly. Accordingly a veryl large take-up occurs at the trailing end of the abrasive sheet where the slack accumulates, while substantially no take-up occurs at the leading end, the little variation occurring there due to movement of the jaws being compensated by stretching of the'abrasive sheet and compression of the backing at the edge.

Inasmuchv as the arrangement herein shown brings the'op'en'ends ofthe jawsalmost to the periphery of the drum when the abrasive sheet'is being secured thereon, as

illustrated in Fig. 2, no large opening in the rum is required andthe opening may be made little larger than the opening of the jaws when inreceiving position. If a large opening is needed to facilitate replacement ofthe parts or for access to the interior'of the drum for other purposes. lip 8'may be removed. As a result of the narrow opening the 4rotation marks on thework are substantially eliminated. A

What I claim and desire to protect by Letters Patent is: f

l. A device of the character described Acomprising aV cylindricaldrum havingan opening in its periphery with edges extending substantially parallel 'to the axis,fclamping means for the ends of a sheet surrounding the drum, said clampingmeans being located inwardlyl lof the opening and opening in alignment therewith, and means yieldingly urging the clampingmeans through a path in which its,` distance from one edge-remains l approximately constant while itsdistance from the other edge varies wherebythe sheet is taken up over the latter edge.

. 2. A device'of the character described comprising 'a cylindrical drum having an opening in its peripheryV with edges' extending Isubstantially parallel tothe axis, clamping means for' vthe ends of a sheet surrounding theV drum, said clamping meansV being pivoted on they drum and ,opening in alignment with the opening in the drum,V and means for yieldingly urging the clamping means about its pivot, said pivot being located so that in the movement of the clamping means its distance from one'edge remains approximately constant .while its distancel from the othery edge varies whereby latter edge. Y x' 8. VA device of thercharacter described comthe-sheet is taken up over the prising a cylindrical drumhavingan opening inits'periphery with 'edges extending sub- 7 stantiallyv parallel to fthe/l axis," clamping means for the ends of a'sheet surrounding the drum, said 'clamping'means being-pivoted on the drum, and means'for yieldingly"urging Cal the clamping means about its pivot, said pivot being located so that the path of movement of the clamping means is across a radius from the center of the pivot to one of said edges, and so that tangente to the path of movement extend in a direction towards the other edge, whereby the sheet is taken up over the latter e ge.

4. A device of the character described comprising a cylindrical drinn having an opening in its periphery with edges extending substantially parallel to the axis, clamping means located inwardly of the opening, said clamping means including a fixed jaw and an adjustable jaw, means for guiding the adj ustable jaw for movement whereby it moves simultaneously lengthwise of and towards or from the fixed jaw, and a screw journalled in one jaw and threaded into the other for moving the adjustable jaw, the axis of the screw extending in the direction of the movement of the adjustable jaw.

In testimony of which invention, I have hereunto set my hand, at Smithville, New Jersey, on this 31st day of May, 1929. j

BRYAN D. PINKNEY. 

